The present invention relates to marine vessels, particularly sailing vessels, and also relates to sail assemblies for sailing vessels.
Boats have been provided heretofore with multiple. spaced-apart hulls or pontoons, the common catamaran and trimaran being typical examples of this approach. Various proposals have been advanced heretofore to employ tetrahedral space frames in construction of multi-hulled sailboats. These tetrahedral space frames typically include a plurality of elongated struts and an elongated mast extending outwardly from a central juncture. The mast extends upwardly from the central juncture, whereas the struts extend outwardly and downwardly from the juncture. Thus, the ends of the mast and of the struts remote from the juncture define the vertices of a tetrahedron. Additional bracing elements interconnect the ends of the struts and mast remote from the juncture, so that these additional elements extend generally along the edges of the tetrahedron. These elements cooperate with the mast, struts and other elements of the vessel to provide a rigid space frame. Pontoons are attached to the strut ends at the three lowermost vertices of the tetrahedron.
Tetrahedral space frame structures of this general nature are disclosed, for example, in U.S. Pat. No. 3,572,740 for use in land yachts and ice boats, and in U.S. Pat. Nos. 3,831,539; 3,991,694; 4,333,412; 4,316,424; 3,631,828 and 4,524,709 for use in water craft. Experiments with another tetrahedral space frame sailboat are described in the article "Amaran, The Mad Hatters Tea Cup At A Gallop!", MULTIHULLS Magazine, July/August 1985, pp. 47-48. Certain of these tetrahedron space frame sailing vessels have provided a basket like enclosure hanging from the space frame beneath the juncture of the spars and mast for occupancy by the crew. Others, as shown in the aforementioned U.S. Pat. Nos. 4,524,709 and 3,572,740 have utilized a sheetlike deck strung beneath the tetrahedral space frame. The tetrahedral space frame concept would appear to have great promise, especially in connection with water-borne sailing vessels. Because the structure is supported at widely spaced apart points on the water surface, it has good stability in rough seas, and extraordinary resistance to the heeling moments caused by wind engaging the sails. Moreover, the mast utilized in the structure of the vessel itself can also serve as part of a sail supporting structure. The basic nature of the tetrahedral space frame would appear to provide good strength for a given weight and size.
The promise of the tetrahedron space frame concept, however, has not been effectively realized heretofore. Tetrahedral space frame sailing vessels heretofore typically have not achieved particularly good strength-to-weight ratios, and typically have been most uncomfortable and inconvenient. Notably, in the case of lightweight sporting and racing sailing vessels for carrying a crew of one or two persons, tetrahedron space frame sailing vessels simply have not been competitive with more conventional monohull and multihull designs. Despite the great theoretical promise of the tetrahedron space frame, the conventional monohull and multihull designs typically have been faster, easier to sail and decidedly more comfortable.
Another theoretically promising concept in sailing vessel development has been the use of multiple, blade-like sails. As disclosed in U.S. Pat. No. 1,504,057, greater propulsive force per unit sail area can be obtained with a large number of elongated, vertically extensive blade-like sails than with a single sail of conventional shape. This concept has been pursued for many years, and is described in more modern form in U.S. Pat. Nos. 4,465,008 and 4,453,483. Typically, the multiple sail blades are arranged in framework of horizontal bars or yards, so that the blades extend vertically between these horizontal bars or yards, or else extend between a single horizontal bar or yard at the top of the assembly and the vessel hull itself. Each blade ordinarily includes framework or beam elements extending along the length of the blade. Typically, the loads imposed by the wind on the blade-like sails are transmitted through the framework or beam elements in the blades to the bars or yards and to the vessel itself.
The multiblade sail concept in theory appears to offer significant performance advantages. Here again, however, the theoretical promise has not been realized in practice. Multiblade sails simply have not been competitive in performance with conventional sails when used on a real boat. Ordinarily, the added weight of the framework in the blades and the associated structures more than offsets any performance gain attainable through the multiblade concept. Moreover, the added weight imposed by the multiblade sail concept is carried far above the center of gravity of the boat, and hence is troublesome with respect to stability, sailing qualities and the like and requires still further added weight in masts or other supporting structures.
Thus, despite the theoretical teachings in the art regarding tetrahedral space frame structures and multiblade sails, there have been needs heretofore for further improvement in vessels and sail assemblies.